MySQL Group Replication is a plugin that enables multi-master replication. It allows any server in the replication group to accept writes and provides automatic recovery from failures or new servers joining. It uses message passing and conflict detection to keep all servers in sync. The plugin manages the distributed transaction execution and recovery process.

1. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. | 1
MySQL Group
Replication
Shivji Jha (shivji.jha@oracle.com)
Software Developer, MySQL Replication Team
2015

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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. | 2

3. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. | 3
Program Agenda
MySQL Group Replication Background
Zoom in: Major Building Blocks
Zoom in: The Complete Stack
Considerations
Summary
1
2
3
4
5

4. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. | 4
Program Agenda
MySQL Group Replication Background
Zoom in: Major Building Blocks
Zoom in: The Complete Stack
Considerations
Summary
1
2
3
4
5

5. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. |
MySQL Replication

MySQL Master server
—
Changes data.
—
Sends changes to Slave.

MySQL Slave server
—
Receives changes from master.
—
Applies received changes to database.
MASTER SLAVE

6. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. |
MySQL (Asynchronous) Replication

Native MySQL Replication: Asynchronous
—
Master executes transaction (T1), commits, ACKs to app, sends to slave.

Fast.

Changes might be lost if master dies.
Master
Slave

7. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. |
MySQL Semi-synchronous Replication
Master
Slave

MySQL-5.5 introduced semi-synchronous replication as a plugin.
—
Extra synchronization step between master and slave.

Point of synchronization configurable on time axis.
—
Master executes, (slave receives, master commits), master ACKs to app.

Slower: Master waits for slave.

Less risk for lost updates.

8. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. |
MySQL Group Replication

Recently: Labs preview of Group Replication based on MySQL-5.7
—
Multi-master update everywhere replication protocol.
—
A set of servers that interact via message passing.
—
(Virtually) synchronous architecture.
Master
Master
Master

9. 9Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. |
MySQL Group Replication
What is MySQL Group Replication ?
“Multi-master update everywhere replication plugin for MySQL
with built-in automatic distributed recovery, conflict detection
and group membership.”
What does the MySQL Group Replication plugin do for the user?
—
Enables update everywhere setup.
—
Provides fault tolerance.

Servers can leave (voluntary or involuntary) and join at any time.

The group self adjusts without any human intervention.
—
Automates group reconfiguration (handling of crashes, failures, re-connects).
—
Implements a replicated Database State Machine.

10. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. |
M M M M M
Write Clients
MySQL
Replication
Environment
MySQL Group Replication

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March, 2015. |
M M M M M
Update ...
Application issues an update.
Group-Based Replication Plugin

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M M M M M
Replication
Events
Application issues an update.
Master executes and multi/broadcasts
the update to the other servers.
Group-Based Replication Plugin

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March, 2015. |
M M M M M
Application issues an update.
Master executes and multi/broadcasts
the update to the other servers.
Servers receive same transaction in the
same order and check for conflicts.
Group-Based Replication Plugin

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March, 2015. |
M M M M M
Application issues an update.
Master executes and multi/broadcasts
the update to the other servers.
Servers receive same transaction in the
same order and check for conflicts.
All servers, independently, decide to
commit the transaction – no conflicts.
Group-Based Replication Plugin

15. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. |
Application issues an update.
Master executes and multi/broadcasts
the update to the other servers.
Servers receive same transaction in the
same order and check for conflicts.
All servers, independently, decide to
commit the transaction – no conflicts.
Originating master replies to the
application.
M M M M M
Group-Based Replication Plugin

16. 16Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. |
MySQL Group Replication is...
… built on top of proven technology!
—
Shares a lot of MySQL Replication infrastructure.
—
Multi-Master approach to replication.
… very interesting, architecturally speaking!
—
The plugin registers as listener to server events.
—
Decoupled from the server core.
—
Provides further decoupling from the communication infrastructure.
… built on reusable components!
—
Layered implementation approach.
—
Interface driven development.

17. 17Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. |
MySQL Group Replication Provides...
… Automatic distributed server recovery!
—
Server that joins the group will automatically synchronize with the others.
—
If a server leaves the group, the others will automatically be informed.
… Multi-master Update Everywhere!
—
Any two transactions on different servers can write to the same tuple. Conflicts
will be detected.
… MySQL/InnoDB look & feel!
—
Load the plugin and start replicating...
—
Monitor group replication stats through Performance Schema tables.

18. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. | 18
Program Agenda
MySQL Group Replication Background
Zoom in: Major Building Blocks
Zoom in: The Complete Stack
Considerations
Summary
1
2
3
4
5

19. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. |
M M M M M
Com. API
Replication
Plugin
API
MySQL
Server
Group Comm.
System (Corosync)
Group Comm.
System (Corosync)
Zoom in: Major Building Blocks

20. 20Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. |
Com. API
Replication
Plugin
API
MySQL
Server
Zoom in: Major Building Blocks
Server calls into the plugin through a generic
interface.
— Server is
 Starting
 Recovering
 Ready to accept connections
 About to commit a transaction etc..
Plugin interacts with the server through a
generic interface.
— Instruct server to
 Commit or abort the ongoing transaction
 Queue transaction in relay log etc..Group Comm.
System (Corosync)
Group Comm.
System (Corosync)

21. 21Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. |
Com. API
Replication
Plugin
API
MySQL
Server
Zoom in: Major Building Blocks
The plugin is responsible for
— Maintaining distributed execution context.
— Detecting conflicts.
— Handling distributed recovery.
 Detect membership changes.
 Donate state if needed.
 Collect state if needed.
— Receiving and handling transactions from other
replicas.
— Sending transactions to other replicas.
— Deciding the fate of on-going transactions.
Group Comm.
System (Corosync)
Group Comm.
System (Corosync)

22. 22Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. |
Com. API
Replication
Plugin
API
MySQL
Server
Zoom in: Major Building Blocks
The communication API is responsible for:
— Decouples the underlaying communication
system from rest of the plugin.
— Mapping the interface to a specific
communication toolkit.
 The Group Replication labs release uses a
corosync binding.
Group Comm.
System (Corosync)
Group Comm.
System (Corosync)

23. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. | 23
Program Agenda
MySQL Group Replication Background
Zoom in: Major Building Blocks
Zoom in: The Complete Stack
Considerations
Summary
1
2
3
4
5

24. 24Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. |
API
Replication
Plugin
API
MySQL
Server
Zoom in: The Complete Stack
Performance Schema Tables: Monitoring
MySQL
APIs: Lifecycle / Capture / Applier
InnoDB
Replication Protocol
Group Comm. API
Corosync
Network
Plugin
Capture Applier
Conflicts
Handler
Group Comm.
System (Corosync)
Group Comm.
System (Corosync)
Group Comm. Binding
Recovery

25. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. | 25
Program Agenda
MySQL Group Replication Background
Zoom in: Major Building Blocks
Zoom in: The Complete Stack
Considerations
Summary
1
2
3
4
5

26. 26Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. |
Current MySQL Group Replication Limitations
Only supports transactional engines (InnoDB).
Limited DDL support. Don't execute concurrently with DML.
Primary Key required on every table.
Requires global transaction identifiers turned on.
Optimistic execution: transactions may abort on COMMIT due to conflicts with
concurrent transactions on other sites.
Upper limit on transaction payload size (due to corosync).

27. 27Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. |
Optimistic Multi-Master Update Everywhere
Observations
 Workload with hotspots => higher abort rates if executed concurrently at different
replicas.
— Any two transactions that have high probability to conflict should execute on
the same replica.
 Better suited for low latency, high-bandwidth networks – LAN.
— Communication latency adds up to the execution time.
— If a replica is “far” away from the rest of the group (in terms of latency), it has
more chances that its transactions are aborted during the conflict detection
phase.
 Large transactions are more likely to exhibit higher conflict.
— Smaller concurrent transactions may commit first thus rendering large
transactions write-sets obsoletes.

28. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. | 28
Program Agenda
MySQL Group Replication Background
Zoom in: Major Building Blocks
Zoom in: The Complete Stack
Considerations
Summary
1
2
3
4
5

29. 29Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. |
Summary
Trendy
—
Great technology for deployments where elasticity is a requirement, such as
cloud based infrastructures
Integrated
—
It is integrated with the server core through a well defined API.
—
It is integrated with GTIDs, row based replication.
—
It is integrated with performance schema tables.
Autonomic and Operations Friendly
—
It is self-healing: no admin overhead for handling server fail-overs.
—
Provides fault-tolerance, enables multi-master update everywhere and a
dependable MySQL service.

30. 30Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. |
Summary
Trendy
—
Great technology for deployments where elasticity is a requirement, such as
cloud based infrastructures
Integrated
—
It is integrated with the server core through a well defined API.
—
It is integrated with GTIDs, row based replication.
—
It is integrated with performance schema tables.
Autonomic and Operations Friendly
—
It is self-healing: no admin overhead for handling server fail-overs.
—
Provides fault-tolerance, enables multi-master update everywhere and a
dependable MySQL service.
MySQL Group Replication is all that... and more! Give it a try and send us
your feedback. You can be part of this story too with your suggestions and
feature requests!

31. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | FOSSASIA 2015 | Singapore, 14th
March, 2015. |
Next Steps: Read about Group Replication

Stay tuned to our blogs from the developers themselves.
http://mysqlhighavailability.com/tag/mysql-group-replication/

Try this out.
http://labs.mysql.com/

Suggest features, find bugs and please do get back to us.
http://bugs.mysql.com/